Treatable traits: toward precision medicine of chronic airway diseases

Airflow obstruction: is it asthma or is it COPD?

Despite the availability of guideline recommendations, diagnostic confusion between COPD and asthma appears common, and often it is very difficult to decide whether the obstruction is caused by asthma or COPD in a patient with airway obstruction. However, there are well-defined features that help in differentiating asthma from COPD in the presence of fixed airflow obstruction. Nonetheless, the presentations of asthma and COPD can converge and mimic each other, making it difficult to give these patients a diagnosis of either condition. The association of asthma and COPD in the same patient has been designated mixed asthma–COPD phenotype or overlap syndrome. However, since the absence of a clear definition and the inclusion of patients with different characteristics under this umbrella term, it may not facilitate treatment decisions, especially in the absence of clinical trials addressing this heterogeneous population. We are realizing that neither asthma nor COPD are single diseases, but rather syndromes consisting of several endotypes and phenotypes, consequently comprising a spectrum of diseases that must be recognized and adequately treated with targeted therapy. Therefore, we must treat patients by personalizing therapy on the basis of those treatable traits present in each subject.

Omalizumab Treatment Response in a Population With Severe Allergic Asthma and Overlapping COPD

BACKGROUND

Asthma and COPD are common airway diseases. Individuals with overlapping asthma and COPD experience increased health impairment and severe disease exacerbations. Efficacious treatment options are required for this population. Omalizumab (anti-IgE) therapy is effective in patients with severe persistent asthma, but limited data are available on efficacy in populations with overlapping asthma and COPD.

METHODS

Data from the Australian Xolair Registry were used to compare treatment responses in individuals with asthma-COPD overlap with responses in patients with severe asthma alone. Participants were assessed at baseline and after 6 months of omalizumab treatment. We used several different definitions of asthma-COPD overlap. First, we compared participants with a previous physician diagnosis of COPD to participants with no COPD diagnosis. We then made comparisons based on baseline lung function, comparing participants with an FEV₁ < 80% predicted to those with an FEV₁ > 80% predicted after bronchodilator use. In the population with an FEV₁< 80%, analysis was further stratified based on smoking history.

RESULTS

Omalizumab treatment markedly improved asthma control and health-related quality of life in all populations assessed based on the Asthma Control Questionnaire and Asthma Quality of Life Questionnaire scores. Omalizumab treatment did not improve lung function (FEV₁, FVC, or FEV₁/FVC ratio) in populations that were enriched for asthma-COPD overlap (diagnosis of COPD or FEV₁ < 80%/ever smokers).

CONCLUSIONS

Our study suggests that omalizumab improves asthma control and health-related quality of life in individuals with severe allergic asthma and overlapping COPD. These findings provide real-world efficacy data for this patient population and suggest that omalizumab is useful in the management of severe asthma with COPD overlap.

Improving the diagnosis of eosinophilic asthma

INTRODUCTION

Diagnosing eosinophilic asthma is important, because uncontrolled eosinophilic airway inflammation is associated with reduced response to glucocorticoids and increased risk of severe exacerbations.

AREAS COVERED

Currently, the diagnosis of eosinophilic asthma is based on measurements of sputum eosinophils, which is time consuming and requires specific technical expertise. Therefore, biomarkers such as blood eosinophils, FeNO, serum IgE and periostin are being used as surrogates. These biomarkers can be used separately or in combination, and their accuracy to detect sputum eosinophilia depends on cut-off values. The demonstration of eosinophils in sputum is no guarantee for response to treatment with current biological agents targeting Type 2 inflammation, because several molecular pathways may lead to eosinophilic inflammation. In the near future, the results of large trials using 'omics' technologies will certainly identify new, more 'upstream' biomarkers of eosinophilic inflammation, that will ultimately lead to the ideal targeted treatment for patients with eosinophilic asthma. Expert commentary: Of currently used surrogate markers to diagnose eosinophilic asthma, blood eosinophils and FeNO have the highest diagnostic accuracy, in particular if used in combination to rule in or rule out eosinophilic asthma. For patients who cannot be classified by these biomarkers alone, the clinical profile may be of help.

Breathomics in the setting of asthma and chronic obstructive pulmonary disease

Exhaled breath contains thousands of volatile organic compounds that reflect the metabolic process occurring in the host both locally in the airways and systemically. They also arise from the environment and airway microbiome. Comprehensive analysis of breath volatile organic compounds (breathomics) provides opportunities for noninvasive biomarker discovery and novel mechanistic insights. Applications in patients with obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease, include not only diagnostics (especially in children and other challenging diagnostic areas) but also identification of clinical treatable traits, such as airway eosinophilia and risk of infection/exacerbation, that are not specific to diagnostic labels. Although many aspects of breath sampling and analysis are challenging, proof-of-concept studies with mass spectrometry and electronic nose technologies have provided independent studies with moderate-to-good diagnostic and phenotypic accuracies. The present review evaluates the data obtained by using breathomics in (1) predicting the inception of asthma or chronic obstructive pulmonary disease, (2) inflammatory phenotyping, (3) exacerbation prediction, and (4) treatment stratification. The current findings merit the current efforts of large multicenter studies using standardized sampling, shared analytic methods, and databases, including external validation cohorts. This will position this noninvasive technology in the clinical assessment and monitoring of chronic airways diseases.

Clinical phenotypes of obstructive airway diseases in an outpatient population

BACKGROUND AND OBJECTIVES

Historically, obstructive airway diseases such as asthma and COPD are classified as different diseases. Although the definitions are clearly described, classification of patients into these traditional, clinical disease entity can be difficult. Recent evidence that there are complex, overlapping phenotypes of obstructive lung disease. Our aim was to capture clinical phenotypes of obstructive diseases through the use of cluster analysis in a representative patient population at a common Dutch pulmonary outpatient clinic. Clinical physiological and cellular/ molecular markers were used in the analysis.

METHODS

To carry out the cluster analysis, an imputed dataset was created from a random sample of 191 adult patients chosen from a pulmonary outpatient clinic. The selection criteria from the sample included patients with a doctor's diagnosis for asthma or COPD. Detailed assessment of patient pulmonary function, blood eosinophil counts, allergic sensitisation and smoking history was collected.

RESULTS

We observed four distinct clusters with different clinical characteristics of obstructive lung diseases. Cluster 1: patients with a history of extensive cigarette smoking, airway obstruction without signs of emphysema; cluster 2: patients with features of the emphysematous type of COPD; cluster 3: patients with characteristics of allergic asthma; cluster 4: patients with features suggesting an overlap syndrome of atopic asthma and COPD.

CONCLUSION

Four phenotypes of obstructive lung disease were identified amongst patients clinically labelled as asthma or COPD. These findings emphasize the concept that there are different phenotypes of obstructive lung diseases, including overlapping and complementary disease entities. These phenotypes of chronic airways disease can serve to tailor disease management.

What is asthma-COPD overlap syndrome? Towards a consensus definition from a round table discussion

Patients with asthma-chronic obstructive pulmonary disease overlap syndrome (ACOS) have been largely excluded from pivotal therapeutic trials and, as a result, its treatment remains poorly defined and lacking firm evidence. To date, there is no universally accepted definition of ACOS, which has made it difficult to understand its epidemiology or pathophysiology. Despite many uncertainties, there is emerging agreement that some of the key features of ACOS include persistent airflow limitation in symptomatic individuals 40 years of age and older, a well-documented history of asthma in childhood or early adulthood and a significant exposure history to cigarette or biomass smoke. In this perspective, we propose a case definition of ACOS that incorporates these key features in a parsimonious algorithm that may enable clinicians to better diagnose patients with ACOS and most importantly enable researchers to design therapeutic and clinical studies to elucidate its epidemiology and pathophysiology and to ascertain its optimal management strategies.

Advancing our understanding of infant bronchiolitis through phenotyping and endotyping: clinical and molecular approaches

INTRODUCTION

Bronchiolitis is a major public health problem worldwide. However, no effective treatment strategies are available, other than supportive care.

AREAS COVERED

Although bronchiolitis has been considered a single disease diagnosed based on clinical characteristics, emerging evidence supports both clinical and pathobiological heterogeneity. The characterization of this heterogeneity supports the concept that bronchiolitis consists of multiple phenotypes or consistent grouping of characteristics. Expert commentary: Using unbiased statistical approaches, multidimentional clinical characteristics will derive bronchiolitis phenotypes. Furthermore, molecular and systems biology approaches will, by linking pathobiology to phenotype, identify endotypes. Large cohort studies of bronchiolitis with comprehensive clinical characterization and system-wide profiling of the '-omics' data (e.g., host genome, transcriptome, epigenome, viral genome, microbiome, metabolome) should enhance our ability to molecularly understand these phenotypes and lead to more targeted and personalized approaches to bronchiolitis treatment.

Do we really need asthma-chronic obstructive pulmonary disease overlap syndrome?

The association of asthma and chronic obstructive pulmonary disease (COPD) in the same patient, which is designated as mixed asthma-COPD phenotype or overlap syndrome (ACOS), remains a controversial issue. This is primarily because many conflicting aspects in the definition of ACOS remain, and it is extremely difficult to summarize the distinctive features of this syndrome. Furthermore, we are realizing that asthma, COPD, and ACOS are not single diseases but rather syndromes consisting of several endotypes and phenotypes and, consequently, comprising a spectrum of diseases. The umbrella term ACOS blurs the lines between asthma and COPD and allows an approach that simplifies therapy. However, this approach contradicts the modern concept according to which we must move toward more targeted and personalized therapies to treat patients with these diseases. Therefore we argue that the term ACOS must be abandoned and ultimately replaced when new phenotypes and underlying endotypes are identified and a new taxonomy of airway diseases is generated.

Holding the Inflammatory System in Check: TLRs and Their Targeted Therapy in Asthma

Inflammation is a complex biological response to detrimental stimuli and can be a double-edged sword. Inflammation plays a protective role in removing pathogenic factors, but dysregulated inflammation is associated with several major fatal diseases such as asthma, cancer, and cardiovascular diseases. Asthma is a complex heterogenous disease caused by genetic and environmental factors. TLRs are the primary proteins associated with the innate and adaptive immune responses to these fatal factors and play an important role in recognizing pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), which initiates the downstream immune response. Due to the complex TLRs cascade and nowadays unsuccessful control in asthma, new studies are focused on TLRs and other potential targets in TLR cascade to minimize airway inflammation.